package org.apache.solr.spelling;

import org.apache.lucene.search.spell.StringDistance;
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import org.apache.lucene.search.spell.SuggestMode;
import org.apache.lucene.search.spell.SuggestWord;
import org.apache.lucene.search.spell.SuggestWordFrequencyComparator;
import org.apache.lucene.search.spell.SuggestWordQueue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.lucene.analysis.Token;
import org.apache.lucene.analysis.core.WhitespaceAnalyzer;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.spell.Dictionary;
import org.apache.lucene.search.spell.LevensteinDistance;
import org.apache.lucene.search.spell.SpellChecker;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.solr.common.params.ShardParams;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.common.params.SpellingParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.core.SolrCore;
import org.apache.solr.schema.FieldType;
import org.apache.solr.search.SolrIndexSearcher;

/**
 * Abstract base class for all Lucene-based spell checking implementations.
 * 
 * <p>
 * Refer to <a
 * href="http://wiki.apache.org/solr/SpellCheckComponent">SpellCheckComponent
 * </a> for more details.
 * </p>
 * 
 * @since solr 1.3
 */
public abstract class AbstractLuceneSpellChecker extends SolrSpellChecker {
	public static final Logger log = LoggerFactory
			.getLogger(AbstractLuceneSpellChecker.class);

	public static final String SPELLCHECKER_ARG_NAME = "spellchecker";
	public static final String LOCATION = "sourceLocation";
	public static final String INDEX_DIR = "spellcheckIndexDir";
	public static final String ACCURACY = "accuracy";
	public static final String STRING_DISTANCE = "distanceMeasure";
	public static final String COMPARATOR_CLASS = "comparatorClass";

	public static final String SCORE_COMP = "score";
	public static final String FREQ_COMP = "freq";

	protected org.apache.lucene.search.spell.SpellChecker spellChecker;

	protected String sourceLocation;
	/*
	 * The Directory containing the Spell checking index
	 */
	protected Directory index;
	protected Dictionary dictionary;

	public static final int DEFAULT_SUGGESTION_COUNT = 5;
	protected String indexDir;
	protected float accuracy = 0.5f;
	public static final String FIELD = "field";

	protected StringDistance sd;

	@Override
	public String init(NamedList config, SolrCore core) {
		super.init(config, core);
		indexDir = (String) config.get(INDEX_DIR);
		String accuracy = (String) config.get(ACCURACY);
		// If indexDir is relative then create index inside core.getDataDir()
		if (indexDir != null) {
			if (!new File(indexDir).isAbsolute()) {
				indexDir = core.getDataDir() + File.separator + indexDir;
			}
		}
		sourceLocation = (String) config.get(LOCATION);
		String compClass = (String) config.get(COMPARATOR_CLASS);
		Comparator<SuggestWord> comp = null;
		if (compClass != null) {
			if (compClass.equalsIgnoreCase(SCORE_COMP)) {
				comp = SuggestWordQueue.DEFAULT_COMPARATOR;
			} else if (compClass.equalsIgnoreCase(FREQ_COMP)) {
				comp = new SuggestWordFrequencyComparator();
			} else {// must be a FQCN
				comp = (Comparator<SuggestWord>) core.getResourceLoader()
						.newInstance(compClass, Comparator.class);
			}
		} else {
			comp = SuggestWordQueue.DEFAULT_COMPARATOR;
		}
		String strDistanceName = (String) config.get(STRING_DISTANCE);
		if (strDistanceName != null) {
			sd = core.getResourceLoader().newInstance(strDistanceName,
					StringDistance.class);
			// TODO: Figure out how to configure options. Where's Spring when
			// you need it? Or at least BeanUtils...
		} else {
			sd = new LevensteinDistance();
		}
		try {
			initIndex();
			spellChecker = new SpellChecker(index, sd, comp);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
		if (accuracy != null) {
			try {
				this.accuracy = Float.parseFloat(accuracy);
				spellChecker.setAccuracy(this.accuracy);
			} catch (NumberFormatException e) {
				throw new RuntimeException(
						"Unparseable accuracy given for dictionary: " + name, e);
			}
		}
		return name;
	}

	@Override
	public SpellingResult getSuggestions(SpellingOptions options)
			throws IOException {
		SpellingResult result = new SpellingResult(options.tokens);
		IndexReader reader = determineReader(options.reader);
		Term term = field != null ? new Term(field, "") : null;
		float theAccuracy = (options.accuracy == Float.MIN_VALUE) ? spellChecker
				.getAccuracy() : options.accuracy;

		int count = Math.max(options.count,
				AbstractLuceneSpellChecker.DEFAULT_SUGGESTION_COUNT);
		for (Token token : options.tokens) {
			String tokenText = new String(token.buffer(), 0, token.length());
			term = new Term(field, tokenText);
			int docFreq = 0;
			if (reader != null) {
				docFreq = reader.docFreq(term);
			}
			String[] suggestions = spellChecker
					.suggestSimilar(
							tokenText,
							((options.alternativeTermCount == null || docFreq == 0) ? count
									: options.alternativeTermCount),
							field != null ? reader : null, // workaround
															// LUCENE-1295
							field, options.suggestMode, theAccuracy);
			if (suggestions.length == 1 && suggestions[0].equals(tokenText)
					&& options.alternativeTermCount == null) {
				// These are spelled the same, continue on
				continue;
			}
			// If considering alternatives to "correctly-spelled" terms, then
			// add the
			// original as a viable suggestion.
			if (options.alternativeTermCount != null && docFreq > 0) {
				boolean foundOriginal = false;
				String[] suggestionsWithOrig = new String[suggestions.length + 1];
				for (int i = 0; i < suggestions.length; i++) {
					if (suggestions[i].equals(tokenText)) {
						foundOriginal = true;
						break;
					}
					suggestionsWithOrig[i + 1] = suggestions[i];
				}
				if (!foundOriginal) {
					suggestionsWithOrig[0] = tokenText;
					suggestions = suggestionsWithOrig;
				}
			}

			if (options.extendedResults == true && reader != null
					&& field != null) {
				result.addFrequency(token, docFreq);
				int countLimit = Math.min(options.count, suggestions.length);
				if (countLimit > 0) {
					for (int i = 0; i < countLimit; i++) {
						term = new Term(field, suggestions[i]);
						result.add(token, suggestions[i], reader.docFreq(term));
					}
				} else {
					List<String> suggList = Collections.emptyList();
					result.add(token, suggList);
				}
			} else {
				if (suggestions.length > 0) {
					List<String> suggList = Arrays.asList(suggestions);
					if (suggestions.length > options.count) {
						suggList = suggList.subList(0, options.count);
					}
					result.add(token, suggList);
				} else {
					List<String> suggList = Collections.emptyList();
					result.add(token, suggList);
				}
			}
		}
		return result;
	}

	protected IndexReader determineReader(IndexReader reader) {
		return reader;
	}

	@Override
	public void reload(SolrCore core, SolrIndexSearcher searcher)
			throws IOException {
		spellChecker.setSpellIndex(index);

	}

	/**
	 * Initialize the {@link #index} variable based on the {@link #indexDir}.
	 * Does not actually create the spelling index.
	 * 
	 * @throws IOException
	 *             If there is a low-level I/O error.
	 */
	protected void initIndex() throws IOException {
		if (indexDir != null) {
			index = FSDirectory.open(new File(indexDir));
		} else {
			index = new RAMDirectory();
		}
	}

	/*
	 * @return the Accuracy used for the Spellchecker
	 */
	@Override
	public float getAccuracy() {
		return accuracy;
	}

	/*
	 * @return the Field used
	 */
	public String getField() {
		return field;
	}

	/*
	 * 
	 * @return the FieldType name.
	 */
	public String getFieldTypeName() {
		return fieldTypeName;
	}

	/*
	 * @return the Index directory
	 */
	public String getIndexDir() {
		return indexDir;
	}

	/*
	 * @return the location of the source
	 */
	public String getSourceLocation() {
		return sourceLocation;
	}

	@Override
	public StringDistance getStringDistance() {
		return sd;
	}

	public SpellChecker getSpellChecker() {
		return spellChecker;
	}
}
